The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Sunset Mock Mirage and Green Flash

Shown above is a complex mock mirage sunset sequence, which I photographed in mid January (2009) from near San Francisco, California. The green flash in frames 2-6 was quite conspicuous. Dispersion in the atmosphere acts to smear the Sun when it's on the horizon, in effect generating separate images of each spectrum color.

Also on the horizon, the atmosphere acts to flatten the apparent solar disk. Light emanating from the bottom of the Sun passes through more of our atmosphere when it is closer to the horizon than does light from the upper reaches of the Sun. The Sun's bottom is thus refracted upwards a greater amount than at the top - this holds for all objects as they approach our horizon.